@KMETE Alsa input error (snd_pcm_open) no such file or directory.... is normal..... as the RPI doesn't have an audio input. You should change the message at the top of the patch to.......
[audio-dialog 0 0 0 0 0 0 0 0 $1 0 0 0 2 0 0 0 44100 25 -1 64(
That will deselect audio input in the Pd audio settings.
Whether that will solve the sticking problem I don't know..... it might.

You seem to now know for sure that audio is stopping.
I will wait for you to find out whether changing the message solves the problem.
David.

@whale-av I connected small usb dongle audio card and for the moment it seems very stable. Not freezing. I get the feeling that indeed it was the built-in headphones output of the pi2B that is not so good apparently.

After many hours of pi running I can confirm the issue was caused by the built-in audio output. Adding the dongle USB audio interface indeed solved it.

@KMETE Excellent news.
David.